Induction pressure or vacuum furnace



Sept. 11, 192s. E. F NORTHRUP 1,683,986

INDUCTION PRESSURE OR VACUUM FURNACE Filed Aug. 1, 1925 Patented Sept. 1l, 1928.

UNITED STATES PATENT oFFIcE."

EDWIN F. NORTHRUP, OF NEAR PRIN CETON NEW JERSEY, ASSIGNOR TO AJAX ELECL TROTHERMIC CORPORATION, OF TRENTON, NEW JERSEY, A CORPORATION OF NEW JERSEY.

INDUCTION PRESSURE Application inea August My invention relates to furnaces for melting or heat treating materials under pressure or vacuum conditions.

The purpose of my invention is to use the furnace coil as the basis for the wall of the furnace. l

A further purpose is to space and insulate between ad'oining turns of a. `progressively wound re erably helical furnace coil by a materia which at the same time closes the spaces against air passage so as to make the coil avallable as the wall of a pressure or vacuum furnace, sealing top and bottom to the wall to complete the furnace.

A further purpose is to to use the hollows in the sides of an edgewise wound iattened hollow conductor as seats for sealing material.

A further purpose'is to provide and preferably cool a greater length of coil than that used as the inductor.

Further purposes will appear in the specification and in the claims.

I have preferred to illustrate by invention by one form only with a modification, selecting a form which is practical, efficient and inexpensive and which at the same time wel] illustrates the principles of my invention.

Figure 1 is a vertical central section of a furnace embodying my invention.

Figure 2 is a fragmentary enlarged section of a portion of the structure seen in Figure 1.

Figure 2a is a section corresponding to Figure 2 of a modification.

In the drawings similar numerals indicate like parts.

In usin the helical furnace coil as a part of the wa for an electric furnace I greatly conserve space and eheapen the construction as my spacing and insulating material is at the same time the sealing material by which vacuum conditions are maintained reducing the quantity ofosealing material required, stiifening and supporting that which is used by the helical conductor and saving the space which would otherwise be required for the sealing medium by spacing it between the turns of the helix.

My furnace comprises to and bottom walls 5 and (i spaced andsea ed between by sidev walls 7. The greater part of the side walls is taken up by a progressively wound` and most desirably helical coil 8 and the spacing insulating and sealing medium 9 beoR VACUUM FURNACE.

1, 1925. 'serial No. 47,5a4.

tween the turns of the coil. Though the coil may obviously be of solid metal, either of such dimension .as to require no cooling or projecting beyond the sealing medium for aircooling as shown in Figure 2a. I prefer a water-cooled.. conductor of the character shown, both because of the highly advantageous cooling effected and because of the assistance which the shape of the coil offers in retaining the sealing medium. With the water-cooled coil shown the water passes through turns of the coil in multiple and for this purpose is shown as entering through pipe 9 and passing out through pipes 10 and 11.

Since the side walls are to kbe made up largely of the coil, I find it desirable, though I not necessary, to use a coil, whether hollow or solid, having greater axial length than that required for the melt. Accordingly in the illustration the electrical connections are shown as made at points 12, 13 intermediate the total length of the coil. Alternating current is applied preferably at. a frequency of three hundred or four hundred or more.

At the top and bottom of the coil I apply rings 11 and 15 and sealing and insulating washers 16 and 17. f

lVhere a hollow conductor has been made by iattening a tube as has been found very desirable, the 1tube can be given the shape shown in the drawing in which the middle portions 18, 19 of the tube 20 lie'closer together than the portions 21, 22 of the tubing giving opposite concave exterior faces 23, which very desirably assist in retaining the spacing, insulating and sealing material 9 against pressure whether from the outside where the interior chamber is to be a vacuum chamber or from the inside when pressure is to be appliedl to the interior. Because of the generation of heat within the melt .and the cooling by which no appreciable increase of temperature takes place within the coil itself, good heatv insulation suiiciently protects the coil from the melt for it to be possible to insulate by rubber which is itself a good seal-- ing medium. Any good cement will also serve the purpose which is dense enough to prevent passage of air. through the cement. Whatever the insulating 'medium it is carried through between the turns and is extended sufficiently over the top and bottom at 24, 25 to form a flat top surface for cooperation with 'terrupted at 25.

rupted to break objectionable continuity of the circuit such as would cause waste of induced current and heating of these plates. The interruption must be filled with a cement or yother filler material to maintain the vacuum orV pressure conditions. The tube and bottom plates are clamped together as by bolts 27 to hold the plates, rings, insulators andV coil together for use and the top plate is removed when access to the furnace is required.

In order to provide for pressure or vacuum within the furnace compartment formed by the structure described a tube 28 is fitted into the upper plate, which tube carries a valve 29 and attachment terminal 30.

The character of crucible or other holder for the material to be melted or heat-treated in the vacuum or under pressure is not controlling as the construction described is capable of operating upon any material placed within it which is electrically conducting whether the charge be placed within an interior container, surrounded merely by sand or be otherwise supported. However, it is quite desirable to supply a heatinsulating shell 31 between the'charge and the coil.

In order that the illustration may be complete and to show a desirable forni of furnace, I show a crucible 32 containing the melt 33 and surrounded by a filler 34, such for example, as pure MgO or zirconium sand which i Supports and heat insulates the Crucible.

' y provi In Figure 2a the coil 8 may be of the character of that shown in my application for patent intended to be filed concurrently with this, entitled Air cooled inductor coil, or may comprise flat strips 35 of solid metal spaced by a ller 9 and extended radially solidly (as distinguished from the spaced projections of that a plication) beyond the filler as at 36 to de additional conductor material, for this reason heating less and cooling better.

' The conductor need be no greater in radial depth than is required for sealing 'against air 'passa e and proper cooling, since the spacing -and iiisulating functions -would be abundantly performed by a much shorter radial depth yof material than is required to insure against air leakage.

Various changes and modifications of my invention will obviously occur to those skilled in the art in view of my disclosure and it is my purpose therefore to claim herein all such as come within the reasonable spirit and scope of my invention.

against air passage, the inductor side wall' comprising the sealing part of the s'ideof the enclosure.

2. A furnace having top and bottom walls and a water cooled inductor side Wall all sealing against air passage. i

3. A furnace having top and bottom walls and an inductor side wall of flat section conductor edgewise wound and all positively sealing againstv air passage.

4. A vacuum or air pressure furnace hav-n ing sealing side walls supported by the inductor coil of the furnace. l

5. An electric furnace inductor adapted to maintain against interior or exterior pressure comprising a wall wound progressively of hollow conductor presenting axially facing concave outer surfaces and a filling material fitting between and sealing against the facing concave surfaces. i

6. A helical furnace inductor coil having spacing and linsulating Afilling protecting against air leakage between the turns of the coil, in combination with a top and a bottom therefor connected with the coil to form a space within capable ofsupporting pressure or vacuum` conditions.

7. An electric induction furnace adapted to maintain pressure or vacuum conditions within the furnace having top and bottom walls and a helical inductor coil between the walls and sealing material between the turns of the coil and between the coil and the top and bottom respectively making the coil a part of the pressure resisting wall of the furnace.

8. An inductor coil having sealing material between the turns of the coil and at the ends of the coil, in combination with a top and bottom for the coil clamping the coil to maintain air tight conditions for the furnace. 9. vA pressure or vacuum furnace comprising an air-tight inductor side wall, top and bottom walls, sealing means between and clamping means for holding the latter to the side walls. l

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10. A furnace havinga water-cooled inhollow conductor, the end portions of the coil being free from electric current, current taps for the coil connected with the coil at a distance from the ends of the coil and water connections for passing water through a greater length than electric current in the coil.

13. In an electric induction furnace, a hollow inductor coil having multiple water connections therewith and a portion of the watercooled coil free from electric current, in combination with current taps for applying the current to the intermediate portion of the coil.

14. In an electric induction furnace, a hollow, flattened, edgewise wound inductor coil having multiple water connections therewith and a portion of the water-cooled coil free from electric current, in combination with current taps for applying the current to the intermediate portion of the coil.

15. In an induction electric furnace, top and bottom walls, a helical coil between them and packing making the coil and the joint between the coil andthe top and bottom walls air tight, in combination with current taps for the coil joining it at a distance from the coil ends.

16. In an induction electric furnace, top and bottom walls, a helical coil between them and packing making the coil and the joint between the coil and the topj and bottom walls air tight, in combination with current taps for the coil joining it at a distance from the coil ends, and water cooling for the coil including that portion of the coil at the ends beyond the taps. v l

EDWIN F. NORTHRUP. 

